Methods, systems, and devices for designing and manufacturing a spinal rod

ABSTRACT

According to the invention, the process includes the steps of: a) taking a sagittal preoperative x-ray of the vertebral column of the patient to be treated, extending from the cervical vertebrae to the femoral heads; b) on that x-ray, identifying points on S1, S2, T12 et C7; c) depicting, on the said x-ray, curved segments beginning at the center of the plate of S1 et going to the center of the plate of C7; e) identifying, on that x-ray, the correction(s) to be made to the vertebral column, including the identification of posterior osteotomies to make; f) pivoting portions of said x-ray relative to other portions of that x-ray, according to osteotomies to be made; g) performing, on said x-ray, a displacement of the sagittal curvature segment extending over the vertebral segment to be corrected; h) from a straight vertebral rod (TV), producing the curvature of that rod according to the shape of said sagittal curvature segment in said displacement position.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/038,694, filed on Jul. 18, 2018, and titled METHODS, SYSTEMS, ANDDEVICES FOR DESIGNING AND MANUFACTURING A SPINAL ROD, which is acontinuation of U.S. patent application Ser. No. 15/694,227, filed onSep. 1, 2017, and titled METHODS, SYSTEMS, AND DEVICES FOR DESIGNING ANDMANUFACTURING A ROD TO SUPPORT A VERTEBRAL COLUMN OF A PATIENT, which isa continuation of U.S. patent application Ser. No. 15/469,302, filed onMar. 24, 2017, and titled METHODS, SYSTEMS, AND DEVICES FOR DESIGNINGAND MANUFACTURING A ROD TO SUPPORT A PATIENT'S VERTEBRAL COLUMN, whichis a continuation of U.S. patent application Ser. No. 15/024,150, filedon Mar. 23, 2016, and titled METHOD MAKING IT POSSIBLE TO PRODUCE THEIDEAL CURVATURE OF A ROD OF VERTEBRAL OSTEOSYNTHESIS MATERIAL DESIGNEDTO SUPPORT A PATIENT VERTEBRAL COLUMN, which is a U.S. national stageentry of PCT Application No. PCT/M2014/065150, filed Oct. 8, 2014, andtitled METHOD MAKING IT POSSIBLE TO ACHIEVE THE IDEAL CURVATURE OF A RODFOR VERTEBRAL OSTEOSYNTHESIS EQUIPMENT DESIGNED TO SUPPORT A PATIENT'SVERTEBRAL COLUMN, which claims priority to and the benefit of FrenchPatent Application No. 1360208, filed Oct. 18, 2013, and titled PROCEDEPERMETTANT DE REALISER LA COURBURE IDEALE D'UNE TIGE D'UN MATERIELD'OSTEOSYNTHESE VERTEBRALE DESTINEE A ETAYER LA COLONNE VERTEBRALE D'UNPATIENT. The entire contents of each of the above-identified patentapplications are incorporated by reference herein and made a part ofthis specification. Any and all priority claims identified in theApplication Data Sheet, or any correction thereto, are herebyincorporated by references under 37 CFR 1.57.

FIELD OF THE INVENTION

The present invention relates to a method making it possible to producethe ideal curvature of a rod for vertebral osteosynthesis equipmentdesigned to correct a patient's vertebral column.

BACKGROUND OF THE INVENTION

It is known to analyze a patient's vertebral column in reference to socalled “pelvic” parameters that are documented in the scientificliterature. The appended FIG. 1 very diagrammatically shows the base ofa vertebral column, i.e., a part of the lumbar vertebrae L and thesacrum S, as well as the femoral heads TF; said pelvic criteria are:

the SS (sacral slope) criterion, which is the incline angle of the plateof S1 (first vertebra of the sacrum), relative to the horizontal;

the PV (pelvic version) criterion, which is the angle formed by thestraight segment connecting the center of the femoral heads TF and thecenter of the plate of S1 with the vertical;

the PI (pelvic incidence) criterion, which is the angle formed by thestraight segment connecting the center of the femoral heads TF and thecenter of the plate of S1 with the perpendicular to the plate of S1.

It is accepted that an individual will adopt a natural vertebral columnposture, called “economic”, avoiding pain and other pathologies, if hispelvic parameters in particular are in agreement with his backmorphotype. If this is not the case, surgical treatment may beconsidered in order to reestablish proper posture of the vertebralcolumn, in which that agreement exists.

It is well known to perform this type of recovery using rigid vertebralrods, in particular metal, fastened to the vertebrae using pediclescrews, which must be curved suitably based on the correction to bedone. The publication of patent application No. WO 98/55038 illustratesan equipment of this type.

It has been shown that imparting the appropriate curvature to a straightrod may be very difficult for a surgeon, the curvature being more orless pronounced in any given location of the rod. Currently, such acurvature is done at the surgeon's discretion and a call greatly on thelatter's experience and dexterity. The trial and error necessary toobtain an appropriate curvature have the significant drawback ofextending the operation time, which is not desirable for the patient,and the risk of implanting a rod with a non-ideal curvature cannot beruled out.

OBJECTS OF THE INVENTION

The present invention aims to resolve this essential drawback.

Patent application publications Nos. WO 2004/017836 A2, US 2009/254326A1 and WO 2008/079546 A2 describe methods not making it possible toachieve the same in a satisfactory manner.

SUMMARY OF THE INVENTION

To achieve that aim, the method according to the invention comprises thefollowing steps:

a) taking a sagittal preoperative x-ray of the vertebral column of thepatient to be treated, extending from the cervical vertebrae to thefemoral heads;

b) on that x-ray, identifying:

the points and straight segments making it possible to calculate theso-called “pelvic” parameters, i.e., the sacral slope, the pelvicversion and the pelvic incidence, the center of the plate of the firstvertebra of the sacrum, called S1;

the center of the second vertebra of the sacrum, called S2;

the center of the lower plate of a reference dorsal vertebra, inparticular the twelfth dorsal vertebra, called T12;

the center of the lower plate of a reference cervical vertebra, inparticular the seventh cervical vertebra, called C7;

c) depicting, on the x-ray, a first curved segment beginning at thecenter of the plate of S1, tangent to the segment going from the centerof S2 to the center of the plate of S1, passing through the centers ofthe bodies of the vertebrae of segment L5-L1 and ending at the center ofthe lower plate of said reference dorsal vertebra;

d) depicting, on the x-ray, a second curved segment tangent to the firstcurved segment at the center of the lower plate of said reference dorsalvertebra, passing through the centers of the bodies of the vertebrae ofthe segment extending between said reference dorsal vertebra and saidreference cervical vertebra and going to the center of the lower plateof said reference cervical vertebra;

e) identifying, on that x-ray, the correction(s) to be made to thevertebral column;

f) pivoting portions of said x-ray relative to other portions of thatx-ray, based on the corrections to be made, so as to show thecorrection(s) to be made to the vertebral column;

g) recalculating said first and second curved segments based on thecorrection(s) made in step f) and depicting those curved segments onsaid x-ray;

h) determining the length of the vertebral segment to be corrected,therefore the length of each vertebral rod to be implanted;

i) for each vertebra of that segment,

either reading, on said x-ray, the distance from the center of the bodyof the vertebra to the posterior face of the pedicle of that vertebra,i.e., the entry face of a pedicle screw in that pedicle; or

reading that same distance in a previously established databank,containing, for each vertebra, the mean value, establishedstatistically, of that distance for the type of patient in question, inparticular based on the age, gender and size of that patient;

j) performing, on said x-ray, a displacement of the sagittal curvaturesegment determined in step g), extending over the vertebral segment tobe corrected determined in step h), over the distances read in step i)for the vertebrae in question, and recalculating the curvature of thatsegment in the displacement position;

k) from a straight vertebral rod, producing the curvature of that rodaccording to the shape of said sagittal curvature segment in saiddisplacement position, recalculated in step j).

The method according to the invention thereby makes it possible toimpart the appropriate curvature to a straight rod easily, that rodbeing fully suitable for the correction to be done.

Preferably, the method also comprises the following steps:

taking a frontal x-ray of the vertebral column of the patient to betreated;

on that x-ray, identifying one or more potential portions of thevertebral column that are curved in the frontal plane, and, for each ofthose curved portions to be straightened, defining a reference point atthe vertebra on which the curved portion begins and a reference point atthe vertebra on which the curved portion ends;

for each of these curved portions, measuring the length of the segmentextending between the reference points identified on that curvedportion;

identifying, on the aforementioned sagittal x-ray, these same referencepoints on these same vertebrae, and identifying the corresponding pointson said sagittal curvature segment; and

performing homothetic stretching of the portion of said sagittalcurvature segment extending between these corresponding points, so as togive that portion a length identical to that existing between saidreference points and to thereby obtain a recalculated sagittal curvaturesegment, taking into account the elongation of the vertebral columnresulting from the correction of that column in the frontal plane.

Preferably, the identification in step e) of the correction(s) to bedone includes either the identification of posterior osteotomies to bedone on the plates of one or more lumbar vertebrae in order to obtain acorrected lumbar curvature, or the determination of the shape of one ormore vertebral implants to be inserted into the intervertebral spaces ofthose vertebrae to obtain that same corrected lumbar curvature, inparticular the determination of the angulation of the wedge shape thoseimplants must have.

Preferably, the method comprises, after step j), the transfer of datarelative to the rod to be produced to a service provider responsible forproducing the curvature of the rod.

Thus, a practitioner, having determined the shape of the rod to beimplanted using the method according to the invention, transfers thedata relative to the rod to be produced to a service providerresponsible for producing the curvature of the rod. Once that curvatureis produced, the service provider will deliver the curved rod to thepractitioner, who will be able to operate on the patient with hisvertebral rod that is ready to be implanted.

The invention will be well understood, and other features and advantagesthereof will appear, in reference to the appended diagrammatic drawing,showing, as a non-limiting example, different steps of the method inquestion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatically view of the base of a vertebral column;

FIG. 2 is a very diagrammatic view of a vertebral column CV as shown onan x-ray, referencing the lumbar lordosis LL, the names of the vertebraeS2-L5 in question, the femoral heads TF, a point situated at the centerof the plate of S1, and the pelvic criteria SS, PV, PI explained abovein reference to FIG. 1;

FIG. 3 is a view similar to FIG. 2, in which the center point of thesecond vertebra of the sacrum, called S2, is shown;

FIG. 4 is a view similar to FIG. 3, in which the center point of thelower plate of the twelfth dorsal vertebra, called T12, is shown;

FIG. 5 is a view similar to FIG. 4, in which the center point of thelower plate of the seventh cervical vertebra, called C7, is shown;

FIG. 6 is a view similar to FIG. 5, in which a first curved segment SC1and a second curved segment SC2 are further shown;

FIG. 7 is a view similar to FIG. 6, in which osteotomies θ1, θ2 to bedone on the upper plates, posterior sides, of vertebrae L4 and L5(fourth and fifth lumbar vertebra) are also shown;

FIG. 8 is a view similar to FIG. 7, showing two portions P1, P2 of thex-ray, delimited by frames, that have been pivoted relative to therespective positions that those same portions occupy in FIG. 7, in thecounterclockwise direction regarding P1 and the clockwise directionregarding P2; these new positions are corrected positions of thevertebral column CV, made possible by the corrected lumbar curvaturemade possible by the osteotomies θ1, θ2 to be done; in order to view thecorrection made, the uncorrected vertebral column, as shown in FIG. 7,is superimposed on the corrected vertebral column shown by FIG. 8, thatuncorrected vertebral column being shown in thin and broken lines;

FIG. 9 is a view similar to FIG. 8, showing, in broken lines, therespective distances DL5 to DT12 which, for each of vertebrae L5 to T12,go from the center of the body of the vertebra to the posterior face ofa pedicle of that vertebra;

FIG. 10 is a view similar to FIG. 9, showing a sagittal curvaturesegment SC that corresponds to the curvature to be given to a vertebralrod to produce the desired correction of the vertebral column;

FIG. 11 is, on the left side of that figure, a view of a plane of thecurved vertebral rod to be obtained, established from said sagittalcurvature segment SC, and, on the right side of that figure, a view ofthe curved vertebral rod TV, obtained from that plane P;

FIG. 12 is, on the left, a partial view of a frontal x-ray RF of thevertebral column of the patient to be treated, and, on the right, a sideview of said sagittal curvature segment SC, on which reference points PCare identified; and

FIG. 13 is a view of a recalculated sagittal curvature segment SCR,obtained following stretching of a portion of the sagittal curvaturesegment SC.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 2 to 11 illustrate a method making it possible to produce theideal curvature of a vertebral rod TV that is a part of a vertebralosteosynthesis equipment, designed to correct a patient's vertebralcolumn by performing a correction of that vertebral column. This methodcomprises the following successive steps:

FIG. 2: taking a sagittal preoperative x-ray RS of the vertebral columnof the patient to be treated, extending from the cervical vertebrae tothe femoral heads, and identifying, on that x-ray RS:

LL: the vertebral segment to be treated;

L1, L2, L3, L4, L5, S1, S2, T12, C7: the first, second, third, fourthand fifth lumbar vertebrae, the first and second vertebrae of thesacrum, the twelfth dorsal vertebra and the seventh cervical vertebra,respectively;

SS, PV, PI: the aforementioned pelvic criteria;

TF: the femoral heads, shown by a circle in the figure;

also identifying, by a dot, the center of the plate of S1.

FIG. 3: identifying, on the x-ray RS, the center of the plate of S2using a dot.

FIG. 4: identifying, on the x-ray RS, the center of the lower plate ofT12 using a dot.

FIG. 5: identifying, on the x-ray RS, the center of the lower plate ofC7 using a dot.

FIG. 6: depicting, on said x-ray RS, said first and second curvedsegments SC1, SC2; the first curved segment SC1 begins at the center ofthe plate of S1, tangent to the segment going from the center of S2 tothe center of the plate of S1, passes through the centers of the bodiesof the vertebrae of segment L5-L1 and ends at the center of the lowerplate of T12; the second curved segment SC2 is tangent to the firstcurved segment SC1 at the center of the lower plate of T12, passesthrough the centers of the bodies of the vertebrae of segment T11-C6 andgoes to the center of the lower plate of C7.

FIG. 7: identifying, on the x-ray RS, the correction(s) of the vertebralcolumn that must be performed, and in particular identifying theosteotomies θ1, θ2 to be done in order to obtain a corrected lumbarcurvature; in the illustrated example, the determination is made toperform an osteotomy θ1 of 10.degree. on the upper plate of L4 and anosteotomy θ2 of 10.degree. on the upper plate of L5.

FIG. 8: pivoting the portions P1 and P2 of the x-ray RS relative to therest of that x-ray RS, based on the osteotomies θ1, 02 to be done; inthe illustrated example, the portion P1 pivots by 10.degree. in thecounterclockwise direction relative to the portion of the x-ray on whichL4 is located (angulation made possible by the osteotomy θ2) and theportion P2 pivots by 10.degree. in the clockwise direction relative tothe portion of the x-ray on which L4 is located (angulation madepossible by the osteotomy θ1). Said first and second curved segments SC1and SC2 are then recalculated based on the correction(s) made and areshown on the x-ray RS.

FIG. 9: the length of the vertebral segment to be corrected isdetermined (in the case at hand, L5-T12), which makes it possible todetermine the length of each vertebral rod TV to be implanted; for eachvertebra of that segment, the respective distances DL5 to DT12 aredetermined from the center of the body of the vertebrae to the posteriorface of a pedicle of that vertebra, i.e., the entry face of a pediclescrew in the pedicle; these distances are either read on the x-ray RS,or are read in a previously established databank, containing, for eachvertebra, the mean value, established statistically, of that distancefor the type of patient in question, in particular based on the age,gender and size of that patient;

FIG. 10: a displacement of the curved segment is then done, on the x-rayRS, over the respective distances DL5 to DT12, and the curvature of thatsegment is recalculated in the displacement position.

FIG. 11: after the diameter of the vertebral rod TV to be used has beendetermined based on the patient in question, a plane P of the curvatureof that rod is established, from which the rod TV is made, by curvaturefrom a straight vertebral rod, in particular by cold bending.

FIGS. 12 and 13 show the following steps that the method may comprise:

FIG. 12:

also taking a frontal x-ray RF of the vertebral column CV of the patientto be treated;

on that x-ray RF, identifying one or more potential portions of thatvertebral column CV that are curved in the frontal plane, and which musttherefore be corrected, and a reference point PRD at the center of thebody of the vertebra on which the curved portion begins and a referencepoint PRF at the center of the body of the vertebra on which the curvedportion ends;

measuring the length of the curved segment extending between thosereference points PRD, PRF;

identifying, on the aforementioned sagittal x-ray RS, these samereference points PRD, PRF on these same vertebrae, and identifying thecorresponding points PC on said sagittal curvature segment SC; and

performing homothetic stretching of the portion of said sagittalcurvature segment SC extending between these corresponding points PC, soas to give that portion a length identical to that separating theaforementioned reference points PRD, PRF.

FIG. 13: a recalculated sagittal curvature segment SCR is thus obtained,taking the elongation of the vertebral column resulting from thecorrection of that column in the frontal plane into account.

The method according to the invention thus has the decisive advantage ofmaking it possible to produce the ideal curvature of a rod for vertebralosteosynthesis equipment designed to correct a patient's vertebralcolumn.

What is claimed is:
 1. A system for generating a specification for apatient-specific implantable spinal rod to correct a vertebral column ofa patient, the system comprising: an electronic interface configured toanalyze one or more preoperative representations of the vertebral columnof the patient, wherein the one or more preoperative representations isanalyzed by: generating one or more modified preoperativerepresentations by correcting a first portion and a second portion ofthe one or more preoperative representations; and preoperativelyobtaining a corrected curvature of the vertebral column of the patient,wherein obtaining the corrected curvature comprises: determining acurvature of a first curved segment of the vertebral column generatedbased on the corrected first portion and the corrected second portion,wherein the first curved segment comprises a portion of the vertebralcolumn below a reference point; and determining a curvature of a secondcurved segment of the vertebral column, wherein the second curvedsegment comprises a portion of the vertebral column above the referencepoint, wherein the second curved segment comprises a different curvaturethan the first curved segment; wherein the electronic interface isfurther configured to: generate preoperative data instructions based atleast in part on the preoperatively obtained corrected curvature of thevertebral column of the patient, the generated preoperative datainstructions configured for use by a manufacturing apparatus tomanufacture the patient-specific implantable spinal rod; andelectronically transfer the generated preoperative data instructions toa manufacturing system for producing the patient-specific implantablespinal rod.
 2. The system of claim 1, wherein the first curved segmentcomprises a representation of sacral vertebrae of the vertebral column.3. The system of claim 1, wherein the first curved segment comprises oneor more representations of one or more vertebrae between L1 to L5. 4.The system of claim 1, wherein the first curved segment comprises one ormore representations of one or more vertebrae between a first vertebraof a sacrum and a lower plate of a reference dorsal vertebra.
 5. Thesystem of claim 4, wherein the first curved segment is tangent to astraight line from a center of a representation of a second vertebra ofthe sacrum to a center of a representation of the first vertebrae of thesacrum.
 6. The system of claim 1, wherein the second curved segmentcomprises a representation of cervical vertebrae of the vertebralcolumn.
 7. The system of claim 1, wherein the second curved segmentcomprises one or more representations of one or more vertebrae betweenC6 to T11.
 8. The system of claim 1, wherein the one or morepreoperative representations of the vertebral column comprises one ormore sagittal x-ray images.
 9. The system of claim 1, wherein the one ormore preoperative representations of the vertebral column comprises oneor more sagittal x-ray images and one or more frontal x-ray images. 10.The system of claim 1, further comprising a computer processor and anelectronic storage medium.
 11. A system for generating a specificationfor a patient-specific spinal rod to correct a vertebral column of apatient, the system comprising: an interface configured to analyze oneor more preoperative representations of the vertebral column of thepatient, wherein the one or more preoperative representations isanalyzed by: generating one or more modified preoperativerepresentations by correcting a first portion and a second portion ofthe one or more preoperative representations; and preoperativelyobtaining a corrected curvature of the vertebral column of the patient,wherein obtaining the corrected curvature comprises: determining acurvature of a first curved segment of the vertebral column generatedbased at least in part on the first portion, wherein the first curvedsegment comprises a portion of the vertebral column below a referencepoint; and determining a curvature of a second curved segment of thevertebral column based at least in part on the second portion, whereinthe second curved segment comprises a portion of the vertebral columnabove the reference point, wherein the second curved segment comprises adifferent curvature than the first curved segment; the interface furtherconfigured to generate the specification for the patient-specific spinalrod based at least in part on the preoperatively obtained correctedcurvature of the vertebral column of the patient, the generatedspecification for the patient-specific spinal rod configured for use byan apparatus to produce the patient-specific implantable spinal rod; andthe interface further configured for transferring the generatedspecification for the patient-specific spinal rod to cause the apparatusto produce a curvature of the patient-specific implantable spinal rod.12. The system of claim 11, wherein the first curved segment comprises arepresentation of sacral vertebrae of the vertebral column.
 13. Thesystem of claim 11, wherein the first curved segment comprises one ormore representations of one or more vertebrae between L1 to L5.
 14. Thesystem of claim 13, wherein the first curved segment comprises one ormore representations of one or more vertebrae between a first vertebraof a sacrum and a lower plate of a reference dorsal vertebra.
 15. Thesystem of claim 14, wherein the first curved segment is tangent to astraight line from a center of a representation of a second vertebra ofthe sacrum to a center of a representation of the first vertebrae of thesacrum.
 16. The system of claim 11, wherein the second curved segmentcomprises a representation of cervical vertebrae of the vertebralcolumn.
 17. The system of claim 11, wherein the second curved segmentcomprises one or more representations of one or more vertebrae betweenC6 to T11.
 18. The system of claim 11, wherein the one or morepreoperative representations of the vertebral column comprises one ormore sagittal x-ray images or frontal x-ray images.
 19. The system ofclaim 11, wherein the one or more preoperative representations of thevertebral column comprises one or more sagittal x-ray images and one ormore frontal x-ray images.
 20. The system of claim 11, furthercomprising a computer processor and an electronic storage medium.